U.S. patent number 5,496,425 [Application Number 08/276,217] was granted by the patent office on 1996-03-05 for cold formed high-strength steel structural members.
This patent grant is currently assigned to Consolidated Metal Products, Inc.. Invention is credited to Hugh M. Gallagher, Jr..
United States Patent |
5,496,425 |
Gallagher, Jr. |
* March 5, 1996 |
**Please see images for:
( Certificate of Correction ) ** |
Cold formed high-strength steel structural members
Abstract
A method of making high-strength steel structural members is
disclosed by providing a blank of high-strength steel having a
ferrite-pearlite microstructure and high-strength mechanical
properties and cold forming the blank by rolling, upsetting,
forging, or extrusion to provide a structural member having a
desired geometric cross-section while the mechanical strength of
the structural member remains substantially the same or greater
than the blank.
Inventors: |
Gallagher, Jr.; Hugh M.
(Cincinnati, OH) |
Assignee: |
Consolidated Metal Products,
Inc. (Cincinnati, OH)
|
[*] Notice: |
The portion of the term of this patent
subsequent to December 17, 2012 has been disclaimed. |
Family
ID: |
23055697 |
Appl.
No.: |
08/276,217 |
Filed: |
July 15, 1994 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
992123 |
Dec 17, 1992 |
5330594 |
|
|
|
848646 |
Mar 9, 1992 |
5236520 |
|
|
|
602675 |
Oct 24, 1990 |
5094698 |
|
|
|
Current U.S.
Class: |
148/651; 72/364;
72/700 |
Current CPC
Class: |
C21D
7/00 (20130101); B21C 23/02 (20130101); C21D
7/10 (20130101); B60G 21/0551 (20130101); F16F
1/14 (20130101); C21D 8/06 (20130101); C21D
8/00 (20130101); B60G 21/055 (20130101); C21D
9/0093 (20130101); C21D 1/02 (20130101); B21B
1/08 (20130101); C21D 7/02 (20130101); C21D
9/02 (20130101); C21D 2211/009 (20130101); Y10S
72/70 (20130101); B60G 2204/44 (20130101); C21D
1/30 (20130101); C21D 2211/008 (20130101); C21D
2211/005 (20130101); C21D 9/0068 (20130101); B60G
2204/1222 (20130101); B60G 2206/427 (20130101); B60G
2204/45 (20130101) |
Current International
Class: |
B21C
23/02 (20060101); B21B 1/08 (20060101); B60G
21/00 (20060101); B60G 21/055 (20060101); F16F
1/14 (20060101); C21D 9/02 (20060101); C21D
8/00 (20060101); C21D 7/00 (20060101); C21D
7/02 (20060101); C21D 1/02 (20060101); C21D
9/00 (20060101); C21D 7/10 (20060101); F16F
1/02 (20060101); C21D 8/06 (20060101); C21D
1/26 (20060101); C21D 1/30 (20060101); C21D
007/02 () |
Field of
Search: |
;72/364,700
;148/651 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0093218A1 |
|
Nov 1983 |
|
EP |
|
2218399 |
|
Feb 1974 |
|
FR |
|
3474743A1 |
|
Apr 1986 |
|
DE |
|
51-144328A |
|
Dec 1976 |
|
JP |
|
58-027958 |
|
Feb 1983 |
|
JP |
|
1535775 |
|
Dec 1978 |
|
GB |
|
Other References
High-Tensile Bolts by Kobe Steel, from Chemical Abstracts No.
101411b, vol. 95 (1981.09) No. 12, Sep. 21, 1981, p. 219. .
A New Microalloyed Multi-Phase Steel for High Strength Cold Heading
Applications by C. I. Garcia, A. K. Lis and A. J. DeArdo, from
Proceedings of the 60th Annual Convention and 1990 Division
Meetings of the Wire Association International Inc., May 1990, pp.
26-30. .
Accelerated Cooling: A Physical Metallurgy Perspective by A. J.
DeArdo, from Canadian Metallurgical Quarterly, vol. 27, No. 2,
1988, pp. 141-154. .
The Deformation Behavior of a Vanadium-Strengthened Dual Phase
Steel by R. G. Davies, from Metallurgical Transactions, vol. 9A,
Jan. 1978, pp. 41-52. .
Warm Working of Steel by Isao Gokyu and Teruo Kishi, from Japanese
Inst. of Metal vol. 9, Supp. 1968. .
Strengthening of Warm-Rolled Low-Carbon Steels by M. L. Bernshtein
and N. V. Filatova, from 2354 Metal Science and Heat Treatment 26,
Feb. 1, 1984, pp. 128-131. .
Materials Science in Engineering, Second Edition by Carl A. Keyser,
1974, pp. 236-237. .
Warm Extrusion of Free-Cutting Steels by E. Nehl, from CA102(22):
888 63K American Chem. Society, 1984..
|
Primary Examiner: Yee; Deborah
Attorney, Agent or Firm: Wood, Herron & Evans
Parent Case Text
RELATED APPLICATIONS
This is a continuation-in-part application of U.S. patent
application Ser. No. 07/992,123 filed Dec. 17, 1992 now U.S. Pat.
No. 5,330,594 which is in turn a continuation in part application
of U.S. patent application Ser. No. 07/848,646, filed Mar. 9, 1992
and now U.S. Pat. No. 5,236,520, which is, in turn, a
continuation-in-part application of U.S. patent application Ser.
No. 07/602,675, filed Oct. 24, 1990 and now U.S. Pat. No.
5,094,698, all assigned to the assignee of this application.
Claims
What is claimed is:
1. A method of making a high-strength steel structural member
having a specific uniform cross-sectional configuration comprising
the steps of:
providing a blank of high-strength steel material having a
ferrite-pearlite microstructure and a tensile strength of at least
about 120,000 psi and a yield strength of at least about 90,000 psi
that comprises by weight:
cold forming said blank by rolling, upsetting, forging or extrusion
to provide a structural member having a uniform cross-sectional
configuration, said uniform cross-sectional configuration including
at least one flange having a thickness less than an overall outer
perimeter of said cross-sectional configuration, said at least one
flange providing increased load bearing capacity to said structural
member, whereby the mechanical properties of tensile strength and
yield strength of said structural member are substantially the same
or greater than said blank.
2. The method of claim 1 wherein said structural member with said
mechanical properties is produced without the need for further
processing steps to improve toughness.
3. The method of claim 1 wherein the high-strength steel material
has previously been hot reduced and cold drawn to provide said
blank.
4. The method of claim 1 wherein the blank of high-strength steel
material has a tensile strength of at least about 150,000 psi and a
yield strength of at least about 130,000 psi.
5. The method of claim 1 wherein the high-strength steel material
comprises, by weight percent:
6. The method of claim 1 wherein the high-strength steel material
comprises, by weight percent:
7. The method of claim 1 wherein said cold forming is carried out
at ambient temperature up to less than about 300.degree. F.
8. The method of claim 1 wherein said structural member with said
mechanical properties is subjected to stress relieving within a
temperature range between about 450.degree. F. to about
1,200.degree. F. in order to modify the physical characteristics of
said structural member.
9. The method of claim 1 wherein said uniform cross-sectional
configuration is selected from the group consisting of O, L, C, Z,
I, T, U, V, and W shapes.
10. A method of making a high-strength steel structural member
having a specific uniform cross-sectional configuration comprising
the steps of:
providing a blank of high-strength steel material having a
ferrite-fine pearlite microstructure, a tensile strength of at
least about 120,000 psi and a yield strength of at least about
90,000 psi, which material has previously been hot reduced and cold
drawn to provide said blank with said high-strength properties,
said high-strength steel comprising, by weight percent:
cold forming said blank by rolling, upsetting or extrusion, at
ambient temperature to provide a structural member having a uniform
cross-sectional configuration, said uniform cross-sectional
configuration including at least one flange having a thickness less
than an overall outer perimeter of said cross-sectional
configuration, said at least one flange providing increased load
bearing capacity to said structural member, said uniform
cross-sectional configuration being selected from the group
consisting of O, L, C, Z, I, T, U, V, and W shapes, whereby the
mechanical properties of tensile strength and yield strength of
said structural member are substantially the same or greater than
said blank.
11. The method of claim 10 wherein said blank of high-strength
steel has a tensile strength of at least about 150,000 psi and a
yield strength of at least about 130,000 psi.
Description
FIELD OF THE INVENTION
The present invention relates to a method of making high-strength
steel structural members, and more particularly, it relates to a
method in which a blank of high-strength steel is cold formed into
a structural member having a desired geometric cross-section, such
that the strength of the member remains substantially the same or
greater than the blank.
BACKGROUND OF THE INVENTION
A number of methods have heretofore been used to make steel parts
and structural members. These methods often employ cold forming
techniques, such as rolling, upsetting, heading and extrusion,
which are well known in the art. In upsetting, the cross-sectional
area of a portion or all of a blank of metal is increased. Heading
is a particular form of upsetting where the blank is a wire, rod or
bar stock. The heads of bolts are often made using heading
techniques. In extrusion, the metal blank is forced through a die
orifice of desired cross-sectional outline to produce a length of
uniform cross section. Rolling includes forming a blank by
repeatedly passing rollers over the length of the blank until it is
formed into the desired shape. Rolling is particularly applicable
for forming elongate structural members having a uniform
cross-sectional configuration over substantially the entire length
of the member.
One such method for making high-strength steel structural members
which is well known begins by annealing or otherwise softening the
steel blank. The annealed steel blank is then cold formed, in a
process which includes one of the above type forming techniques,
into a desired geometric cross-section. The now formed structural
member is then heat treated, i.e., austenitized, hardened by
quenching followed by tempering, to obtain the high-strength
mechanical properties desired. The steel material of the resulting
member has a tempered martensite microstructure. The mechanical
properties produced from such heat treatments are often
inconsistent and can vary widely from member to member. In
addition, the annealing and heat treating steps significantly add
to the cost of the overall process for making the high-strength
steel structural members, due in large part to the energy
consumption associated with heating the member and the required
labor and processing.
In another method for making such high-strength steel structural
members, the blank of steel is initially austenitized, hardened by
quenching and then tempered to the point where the mechanical
properties of the post-heat treated blank are such that the blank
can be subsequently cold formed, in a process which includes one of
the above forming techniques, into a desired geometric
cross-section. The steel material of the finished member from this
method also has a tempered martensite microstructure. While this
method apparently has advantages over the previously described
method in that narrower strength tolerances from member to member
have reportedly been obtained, this method still employs a costly
heat treating process.
Cold forming blanks of high-strength material is known. In U.S.
Pat. No. 3,904,445 issued to the present inventor, a method is
disclosed for cold forming a length of high-strength steel bar
stock into a U-bolt. The '445 patent discloses such a length of bar
stock made of a steel material having a composition consisting
essentially of, by weight percent: carbon between about 0.50-0.55%,
manganese between about 1.20-1.65%, vanadium between about
0.03-0.05 %, with the balance substantially all iron. However, cold
forming a bend in a length of bar stock is less severe than other
cold forming techniques, such as upsetting and extruding. Until
this invention, it was thought that cold forming a blank of
high-strength into a part or structural member by upsetting or
extrusion type techniques would likely result in the formation of
cracks or even fractures in the finished product or at the least
would likely require the gradual formation of the member by a
series of cold forming steps with an annealing or stress relieving
step performed between successive cold forming operations. Such
cracks or fractures would likely ruin the member. In addition,
employing such cold forming and annealing steps would add to the
time and cost of making such high strength steel structural
members.
SUMMARY OF THE INVENTION
There has heretofore been lacking a method of making a
high-strength steel structural member from a blank of steel having
a ferrite-pearlite microstructure and possessing desired
high-strength properties, which method includes a cold forming step
whereby the blank is cold formed by rolling, upsetting, forging, or
extrusion type techniques into a desired structural member, with
the mechanical strength of the member remaining substantially the
same or greater than the strength originally possessed by the
blank, and with the member produced with the desired high-strength
mechanical properties without the need of heat treatment.
The term "blank" as used herein has its usual meaning, i.e., a
piece of metal to be formed into a finished member of desired
geometric cross-section. Blanks include such pieces of metal as
rods, wires, bar stock and cut lengths thereof (i.e., a piece of
steel long in proportion to its width or thickness). A blank is
differentiated from a structural member in that a structural member
has at least one flange included in its cross-sectional
configuration. The flange is a member which has a thickness less
than an overall outer dimension of the cross-sectional
configuration and provides increased load beating capability to the
structural member.
The present invention is directed to a method of making
high-strength steel structural members from blanks of high-strength
steel material having a ferrite-pearlite microstructure and a
tensile strength of at least about 120,00 psi and a yield strength
of at least about 90,000 psi with the following composition by
weight percent: carbon--about 0.30 to about 0.65%, manganese--about
0.30 to about 2.5 %, at least 1 grain refiner from the group
consisting of aluminum, niobium (i.e., columbium), titanium and
vanadium and mixtures thereof, in an amount effective up to about
0.35 %, and iron--balance.
In one of its aspects, the present invention provides a method of
making high-strength steel structural members from such blanks by
cold forming the blank using techniques such as rolling, upsetting,
forging, or extrusion to provide a member having the desired
geometric cross-section with a ferrite-pearlite microstructure,
whereby the mechanical properties of tensile strength and yield
strength of the member are substantially the same or greater than
the blank.
The present invention also provides a method of making
high-strength steel structural members which includes cold forming
a blank of high-strength steel using such techniques, whereby the
mechanical properties of tensile strength and yield strength are
substantially the same or greater than the blank and wherein the
member, with the desired mechanical properties of tensile strength
and yield strength, is produced without the need for further
processing steps to improve toughness. Depending at least in part
on its geometric cross-section, some members may need to be stress
relieved within a temperature range of between about 450.degree. F.
to about 1,200.degree. F. in order to raise, lower, or otherwise
modify the mechanical properties of the steel member (e.g., tensile
strength, yield strength, percent elongation, hardness, percent
reduction of area, etc.).
The principles of this invention, its objectives and advantages
will be further understood with reference to the following detailed
description.
DETAILED DESCRIPTION OF THE INVENTION
The method of the present invention is useful for producing a wide
variety of finished high-strength steel structural members. In
particular, elongated high strength steel structural members having
a uniform cross-sectional configuration over substantially its
entire length. For example, structural members having an O, L, C,
Z, I, T, W, U, V shapes and other members are susceptible to
forming by the cold forming process are described herein.
A blank is distinguished herein from a structural member in that a
structural member is elongate with a uniform cross-sectional
configuration which includes at least one flange. The flange is a
member which has a thickness less than an overall outer dimension
of the cross-sectional configuration (i.e., the width, height, or
outer diameter of the structural member). The flange distinguishes
the structural member from a blank in that the flange provides
increased load beating capability to the member. In other words,
the structural member has more load bearing capability with the
flange than a member without the flange having the same material
composition and properties as the structural member. The load may
be axial as in an end-on load, lateral as in a side load or any
other type of load applied to the structural member. The flange is
integrally formed either continuously or discontinuously with
respect to the remainder of the structural member. Examples of
discontinuous flanges are the upper and lower portions of an
I-shaped beam with respect to the center portion of the I-beam, or
of either leg of an L-shaped truss with respect to the other leg of
the truss. An example of a continuous flange is any cord or portion
of the cross-sectional configuration of an O-shaped structural
member. Examples of structural members having at least one flange
are O, L, C, Z, I, T, U, V, and W shaped members.
In a preferred embodiment, the method of the present invention for
making a high-strength steel structural member includes providing a
blank of high-strength steel material having a microstructure of
fine pearlite in a ferritic matrix, a tensile strength of at least
about 120,000 psi and preferably at least about 150,000 psi, and a
yield strength of at least about 90,000 psi, and preferably at
least about 130,000 psi. Pearlitic constituents are generally
considered to be "fine" when their lamellae are not resolvable at
an optical magnification of about 1000 times. In one form, the
high-strength steel material utilized as the blank has been hot
reduced and cold drawn to provide the blank having the mechanical
properties of tensile strength and yield strength stated above.
The high-strength steel material used to make the blank has the
following composition, by weight percent:
______________________________________ carbon about 0.30 to about
0.65% manganese about 0.30 to about 2.5% at least 1 ferrous grain
refiner from the group consisting of aluminum, niobium, titanium
and vanadium, and mixtures thereof, in an effective amount up to
about 0.35% iron balance.
______________________________________
In a more preferred form, the high-strength steel material has the
following composition, by weight percent:
______________________________________ carbon about 0.40 to about
0.55% manganese about 0.30 to about 2.5% at least one ferrous grain
refiner from the group consisting of aluminum, niobium, titanium
and vanadium and mixtures thereof in an effective amount up to
about 0.20% iron balance.
______________________________________
In a still more preferred form, the high-strength steel material
has the following composition, by weight percent:
______________________________________ carbon about 0.50 to about
0.55% manganese about 1.20 to about 1.65% at least 1 ferrous grain
refiner from the group consisting of aluminum, niobium, titanium
and vanadium, and mixtures thereof, in an effective amount from
about 0.03 to about 0.20% iron balance.
______________________________________
While aluminum, niobium (i.e., columbium), titanium and vanadium
act as grain refiners, vanadium is the most preferred of the grain
refiners. Furthermore, it should be understood that the
compositions listed and claimed herein may include other elements
which do not impact upon the practice of this invention.
The blank, having a composition and mechanical properties of
tensile strength and yield strength as given above is thereafter
cold formed using such techniques as upsetting, forging, or
extrusion at a temperature between ambient or room temperature up
to less than about 300.degree. F., and preferably at about ambient
temperature, to provide a member having a desired geometric
cross-section, whereby the mechanical properties of tensile
strength and yield strength of the member are substantially the
same or greater than the blank. The formed member, with the
mechanical properties of tensile strength and yield strength given,
is preferably produced without the need for further processing
steps, such as a final stress relieving step, to improve toughness.
However, for certain geometric cross-sections and applications of
the member, a stress relieving step may be necessary.
The blank of high-strength steel material having a tensile strength
of at least about 120,000 psi and a yield strength of at least
90,000, which is used as the starting piece in the method of the
present invention, is produced by any suitable method known in the
art. One such method is disclosed in U.S. Pat. No. 3,904,445 to the
present inventor and the specification in its entirety is
incorporated herein by reference. The '445 patent discloses a
processing sequence to produce a high-strength steel bar stock of
the type particularly useful for producing threaded fasteners,
including U-bolts. In the described process, the bar stock produced
has a fine grained structure between about ASTM No. 5-8. In the
disclosed process, a steel, having a composition falling within
certain disclosed ranges, is subjected to a standard hot reducing
operation to within 10%-15% of final gauge. The hot reduced bar
stock is then cut or severed into individual lengths for rapid air
cooling. Thereafter, the individual lengths of hot reduced bar
stock are subjected to a cold finishing to final gauge. The final
step is a controlled stress relieving step to increase the
mechanical strength properties. This stress relieving step
comprises heating the lengths of bar stock to between about
500.degree.-850.degree. F. for about one hour, but may or may not
be necessary. Thus, such bar stock, with and without further stress
relieving may be used to form the starting high-strength steel
blank.
The following example illustrates the practice of the present
invention to produce a structural member from high-strength steel
bar stock produced in accordance with the method disclosed in U.S.
Pat. No. 3,904,445 described above.
EXAMPLE
High-strength 1552 steel I-beam stock had the following composition
by weight:
______________________________________ Carbon 0.52% Manganese 1.43%
Phosphorous 0.009% Sulphur 0.017% Silicon 0.22% Vanadium 0.075%
Chromium 0.05% Molybdenum 0.01% Iron balance.
______________________________________
A center section of the stock had a thickness of 0.177" and each
top and bottom flange had a thickness of about 0.16". The overall
height of the stock I-beam was 2.64" and the overall width was the
same width as each flange, specifically 1.825". A 0.125" radius
fillet joined each face of the center section or web to each
flange. The I-beam stock was sectioned into approximately 3 foot
lengths. The stock was tested to have a tensile strength of 133,000
psi and a yield strength of 89,000 psi.
The I-beam stock was extruded through a tapered die with 65,000 lbs
of force at room temperature to cold form a finished I-beam
structural member. The cold formed I-beam had an overall width of
1.825" and an overall height of 2.64". A center section of the
1-beam was 0.16" thick and extended between a pair of spaced 0.155"
thick top and bottom flanges. Therefore, the thickness of each
flange (0.155") is less than an overall outer dimension of the
beam, i.e., the width (1.825") or the height (2.64"). A 0.125"
radius fillet was formed onto each face of the juncture between the
center section or web and the top and bottom flanges. The cold
formed I-beam was tested to have a tensile strength of 142,000 psi
and yield strength of 118,000 psi.
The mechanical properties of tensile strength and yield strength of
the finished I-beam structural member are greater than that
originally possessed by the bar stock, and therefore, no further
strengthening processing steps are required. The finished member
also has enough of the desired mechanical property of ductility
originally possessed by the bar stock that the need for further
processing steps to improve toughness can generally be eliminated.
However, for certain uses of the I-beam structural member, a stress
relieving step may be necessary.
Compared to prior methods which used a heat treating process (i.e.,
austenitizing, hardening by quenching and tempering), especially
when the heat treatment was used after cold forming to produce the
desired high-strength mechanical properties of the member, finished
structural members made according to the present invention are more
likely to consistently have mechanical properties which fall within
a narrower range. Thus, the present invention is more likely to
consistently produce structural members with higher strength levels
and within a narrower range.
The scope of the present invention is not intended to be limited by
the examples provided herein, but rather as defined by the appended
claims.
* * * * *